A technique called photelectron spectroscopy is used to measure the I.P of atoms. A same is irradiated with U.V light, and electrons are ejected from the valence shell. The kinetic energy of the ejected electrons are measured. Since, the energy of the U.V. photon and the kinetic energy of the ejected electrons are known, we can write
` hv = I.P. + (1)/(2) m u^(2)`
Where v is the frequency of the U.V light, and m and u are mass and velocity of the electron respectively. In one experiment the kinetic energy of the ejected electron from potassium is found to be. `5.34 xx 10^(-19) J` using U.V. source of wavelength 162 nm. Calculate I.E. of potassium ` (h = 6.62 xx 10^(-34) J-s, c= 3 xx 10^(8) m " / " s)`.